Prime Minister Narendra Modi on Wednesday announced that India had demonstrated anti-satellite missile capability by shooting down a live satellite. Addressing the nation, the Prime Minister said India's action was not directed against any country. Shooting down a low earth orbit satellite is a rare achievement for the country, he said. Let us examine the science behind Mission Shakti which has given India a place among the world's elite space powers.
What is a low earth orbit satellite?
This is an earth-centred orbit with an altitude of 2000 km or less. These satellites move at a speed of 7.8 km/sec. The speed is reduced with an increase in orbital altitude. A satellite needs the lowest amount of energy for being placed into a low earth orbit. These satellites are commonly used for communication purposes such as Iridium Communication Satellites. One of the quintessential LEOs functional is the Hubble Space Telescope which orbits at about 540 km above the earth.
These satellites are hard to locate as their position in orbit changes continuously. Also, they observe and communicate over a very small area of the earth.
What are ASATs?
Anti-satellite missiles or ASATs are missiles specifically designed to destroy satellites for strategic purposes. Several nations have operational ASAT systems but have not used them in warfare.
In 2010. the Defense Research and Development Organisation (DRDO) had announced that India was developing the exo-atmospheric kill vehicle technology that could be combined to a weapon to destroy enemy satellites in orbit.
In 2012, VK Saraswat, the then chief of the DRDO, announced that India has all the building blocks in place to integrate an anti-satellite weapon to neutralize hostile satellites in low earth and polar orbits.
History of ASATs and their legality
Anti-satellite tests are extremely controversial and considered to be contributing towards weaponisation of space, which is prohibited by the Outer Space Treaty of 1967. Hence PM Modi was careful to mention that the missile test does not violate any international treaty and is a “defensive” move, aimed at securing its space infrastructure, and does not change India’s strong opposition to the weaponisation of space.
In January 2007, China destroyed its dysfunctional satellite with an SC-19 ASAT missile with a kinetic warhead. In January 2008, an American reconnaissance satellite which went out of orbit was shot down by the US with a RIM-161 Standard Missile 3 Anti-Ballistic Missile.
Russia is the only country to have test-fired ASAT missiles unlike other nations who fired them to shoot down out of orbit satellites. In November 2015, Russia successfully test-fired its direct-ascent anti-satellite missile, known as PL-19 Nudol. Russia reportedly test-fired the Nudol four more times since then, the last being in December 2018.